The present invention relates to a vehicle tire, more particularly to an improved tread rubber suitable for pneumatic tires which is capable of improving dry grip performance and wet grip performance.
In recent years, a tire whose tread rubber is reinforced mainly by silica instead of conventional carbon black has been proposed in order to improve the rolling resistance and wet: grip performance of the tire.
The silica-reinforced rubber has a low energy loss property, suppleness and suitable adhesiveness to the wet road surface. Thus it can improve the rolling resistance and wet grip performance.
In such a tread rubber, however, dry grip performance inevitably decreases. Therefore, a lot of effort was put into finding a combination of a silica content and a carbon black content by which a good balance of dry grip performance and; wet grip performance can be obtained.
However, if the silica content exceeds a certain value, the silica hinders the carbon black from displaying its full function. Further, if the carbon black content exceeds a certain value, the carbon black hinders the silica from displaying its full function. Therefore, there are limits to improving the dry grip performance and wet grip performance by adjusting the silica content and carbon black content.
It is therefore, an object of the present invention to provide a vehicle tire of which dry grip performance, wet grip performance and the like are effectively improved by avoiding the above-mentioned problems.
According to the present invention, a vehicle tire comprises
a tread rubber which forms a ground contacting face of the tire,
the tread rubber, in a range from the ground contacting face to a certain depth, comprising circumferentially extending wide parts made of a carbon-black-reinforced rubber composition and circumferentially extending narrow parts made of a silica-reinforced rubber composition, which wide parts and narrow parts alternate in the tire axial direction,
the axial width of each of the narrow parts being in the range of from 0.5 to 1.5 mm, and
the number of the narrow parts counted across a ground contacting width of the ground contacting face being in a range of from 3 to 11.